This invention relates to an improvement to an image forming apparatus and also to an image forming method adapted to forming an image on both sides of a sheet of copying paper.
As is well known, it is highly important for an image forming apparatus of the above identified type that it can effectively eliminate any mis-registration between the image formed on the front surface of a sheet of copying paper and the image formed on the rear surface of the sheet.
Japanese Patent Application Laid-Open No. 2000-147842 describes a method of synchronizing the printing operation of the front surface printing mechanism adapted to continuously printing an image on the front surfaces of a number of sheets of copying paper and that of the rear surface printing mechanism adapted to continuously printing another image on the rear surfaces of the sheets of copying paper in a controlled way.
However, the technology of eliminating any mis-registration between the images formed on the opposite surfaces of a sheet of copying paper, including the above described known method, is still on the way toward perfection. In other words, any known techniques in the technological field under consideration are accompanied by the problem of a large and complex apparatus that operates in a complex way and does not provide a level of reliability required for practical applications.
In view of the above identified circumstances, it is therefore the object of the present invention to provide an image forming apparatus and an image forming method that can highly reliably eliminate any mis-registration of the images formed on the opposite surfaces of a sheet of copying paper and hence are adapted to practical applications.
In an aspect of the present invention, the above object is achieved by providing an image forming apparatus adapted to forming images on the opposite surfaces of a sheet of recording paper, the apparatus comprising a control means for controlling the location of the image formed on one of the opposite surfaces of the sheet of recording paper in correspondence to the location of the image formed on the other surface of the sheet of recording paper.
In another aspect of the invention, there is also provided an image forming apparatus having a first image forming means for feeding a sheet of recording paper and forming an image on one of the opposite surfaces of the sheet and a second image forming means for feeding the sheet of recording paper carrying the image formed by the first image forming means on one of the opposite surfaces of the sheet and forming another image on the other surface of the sheet.
The image forming apparatus comprises a time measuring means for measuring the time period from the time when the operation of forming an image on one of the opposite surfaces of the sheet of recording paper of the first image forming means starts to the time when the tail end of the sheet of recording paper passes a predetermined detecting position and a control means for controlling the time of starting the operation of forming another image on the opposite surface of the sheet of recording paper of the second image forming means on the basis of the time period measured by the measuring means.
In still another aspect of the invention, there is provided an image forming method of forming images on the opposite surfaces of a sheet of recording paper, the method comprising a control step for controlling the location of the image formed on one of the opposite surfaces of the sheet of recording paper in correspondence to the location of the image formed on the other surface of the sheet of recording paper.
In a further aspect of the invention, there is provided an image forming method having a first image forming step of feeding a sheet of recording paper and forming an image on one of the opposite surfaces of the sheet and a second image forming step of feeding the sheet of recording paper carrying the image formed by the first image forming means on one of the opposite surfaces of the sheet and forming another image on the other surface of the sheet.
The image forming method comprises a time measuring step for measuring the time period from the time when the operation of forming an image on one of the opposite surfaces of the sheet of recording paper of the first image forming step starts to the time when the tail end of the sheet of recording paper passes a predetermined detecting position and a control step of controlling the time of starting the operation of forming another image on the opposite surface of the sheet of recording paper of the second image forming step on the basis of the time period measured by the measuring means.
Since the above described arrangements and methods are adapted to control the location of the image formed on one of the opposite surfaces of the sheet of recording paper in correspondence to the location of the image formed on the other surface of the sheet of recording paper, they can highly reliably eliminate any mis-registration of the images formed on the opposite surfaces of a sheet of copying paper so that the images formed on the opposite surfaces of a sheet of recording paper can be accurately registered relative to each other.